﻿// SimplexNoise for C#
// Author: Heikki Törmälä

//This is free and unencumbered software released into the public domain.

//Anyone is free to copy, modify, publish, use, compile, sell, or
//distribute this software, either in source code form or as a compiled
//binary, for any purpose, commercial or non-commercial, and by any
//means.

//In jurisdictions that recognize copyright laws, the author or authors
//of this software dedicate any and all copyright interest in the
//software to the public domain. We make this dedication for the benefit
//of the public at large and to the detriment of our heirs and
//successors. We intend this dedication to be an overt act of
//relinquishment in perpetuity of all present and future rights to this
//software under copyright law.

//THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
//EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
//MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
//IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
//OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
//ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
//OTHER DEALINGS IN THE SOFTWARE.

//For more information, please refer to <http://unlicense.org/>


namespace SimplexNoise {
	/// <summary>
	/// Implementation of the Perlin simplex noise, an improved Perlin noise algorithm.
	/// Based loosely on SimplexNoise1234 by Stefan Gustavson <http://staffwww.itn.liu.se/~stegu/aqsis/aqsis-newnoise/>
	/// 
	/// </summary>
	public class Noise {
		/// <summary>
		/// 1D simplex noise
		/// </summary>
		/// <param name="x"></param>
		/// <returns></returns>
		public static float Generate(float x) {
			int i0 = FastFloor(x);
			int i1 = i0 + 1;
			float x0 = x - i0;
			float x1 = x0 - 1.0f;
			float n0, n1;
			float t0 = 1.0f - x0 * x0;
			t0 *= t0;
			n0 = t0 * t0 * grad(perm[i0 & 0xff], x0);
			float t1 = 1.0f - x1 * x1;
			t1 *= t1;
			n1 = t1 * t1 * grad(perm[i1 & 0xff], x1);
			// The maximum value of this noise is 8*(3/4)^4 = 2.53125
			// A factor of 0.395 scales to fit exactly within [-1,1]
			return 0.395f * (n0 + n1);
		}

		/// <summary>
		/// 2D simplex noise
		/// </summary>
		/// <param name="x"></param>
		/// <param name="y"></param>
		/// <returns></returns>
		public static float Generate(float x, float y) {
			const float F2 = 0.366025403f; // F2 = 0.5*(sqrt(3.0)-1.0)
			const float G2 = 0.211324865f; // G2 = (3.0-Math.sqrt(3.0))/6.0
			float n0, n1, n2; // Noise contributions from the three corners
			// Skew the input space to determine which simplex cell we're in
			float s = (x + y) * F2; // Hairy factor for 2D
			float xs = x + s;
			float ys = y + s;
			int i = FastFloor(xs);
			int j = FastFloor(ys);
			float t = (float)(i + j) * G2;
			float X0 = i - t; // Unskew the cell origin back to (x,y) space
			float Y0 = j - t;
			float x0 = x - X0; // The x,y distances from the cell origin
			float y0 = y - Y0;
			// For the 2D case, the simplex shape is an equilateral triangle.
			// Determine which simplex we are in.
			int i1, j1; // Offsets for second (middle) corner of simplex in (i,j) coords
			if(x0 > y0) {
				i1 = 1;
				j1 = 0;
				// lower triangle, XY order: (0,0)->(1,0)->(1,1)
			} else {
				i1 = 0;
				j1 = 1;
				// upper triangle, YX order: (0,0)->(0,1)->(1,1)
			}
			// A step of (1,0) in (i,j) means a step of (1-c,-c) in (x,y), and
			// a step of (0,1) in (i,j) means a step of (-c,1-c) in (x,y), where
			// c = (3-sqrt(3))/6
			float x1 = x0 - i1 + G2; // Offsets for middle corner in (x,y) unskewed coords
			float y1 = y0 - j1 + G2;
			float x2 = x0 - 1.0f + 2.0f * G2; // Offsets for last corner in (x,y) unskewed coords
			float y2 = y0 - 1.0f + 2.0f * G2;
			// Wrap the integer indices at 256, to avoid indexing perm[] out of bounds
			int ii = i % 256;
			int jj = j % 256;
			// Calculate the contribution from the three corners
			float t0 = 0.5f - x0 * x0 - y0 * y0;
			if(t0 < 0.0f)
				n0 = 0.0f;
			else {
				t0 *= t0;
				n0 = t0 * t0 * grad(perm[ii + perm[jj]], x0, y0); 
			}
			float t1 = 0.5f - x1 * x1 - y1 * y1;
			if(t1 < 0.0f)
				n1 = 0.0f;
			else {
				t1 *= t1;
				n1 = t1 * t1 * grad(perm[ii + i1 + perm[jj + j1]], x1, y1);
			}
			float t2 = 0.5f - x2 * x2 - y2 * y2;
			if(t2 < 0.0f)
				n2 = 0.0f;
			else {
				t2 *= t2;
				n2 = t2 * t2 * grad(perm[ii + 1 + perm[jj + 1]], x2, y2);
			}
			// Add contributions from each corner to get the final noise value.
			// The result is scaled to return values in the interval [-1,1].
			return 40.0f * (n0 + n1 + n2); // TODO: The scale factor is preliminary!
		}

		public static float Generate(float x, float y, float z) {
			// Simple skewing factors for the 3D case
			const float F3 = 0.333333333f;
			const float G3 = 0.166666667f;
			float n0, n1, n2, n3; // Noise contributions from the four corners
			// Skew the input space to determine which simplex cell we're in
			float s = (x + y + z) * F3; // Very nice and simple skew factor for 3D
			float xs = x + s;
			float ys = y + s;
			float zs = z + s;
			int i = FastFloor(xs);
			int j = FastFloor(ys);
			int k = FastFloor(zs);
			float t = (float)(i + j + k) * G3; 
			float X0 = i - t; // Unskew the cell origin back to (x,y,z) space
			float Y0 = j - t;
			float Z0 = k - t;
			float x0 = x - X0; // The x,y,z distances from the cell origin
			float y0 = y - Y0;
			float z0 = z - Z0;
			// For the 3D case, the simplex shape is a slightly irregular tetrahedron.
			// Determine which simplex we are in.
			int i1, j1, k1; // Offsets for second corner of simplex in (i,j,k) coords
			int i2, j2, k2; // Offsets for third corner of simplex in (i,j,k) coords
			/* This code would benefit from a backport from the GLSL version! */
			if(x0 >= y0) {
				if(y0 >= z0) {
					i1 = 1;
					j1 = 0;
					k1 = 0;
					i2 = 1;
					j2 = 1;
					k2 = 0;
				} // X Y Z order
                else if(x0 >= z0) {
					i1 = 1;
					j1 = 0;
					k1 = 0;
					i2 = 1;
					j2 = 0;
					k2 = 1;
				} // X Z Y order
                else {
					i1 = 0;
					j1 = 0;
					k1 = 1;
					i2 = 1;
					j2 = 0;
					k2 = 1;
				} // Z X Y order
			} else { // x0<y0
				if(y0 < z0) {
					i1 = 0;
					j1 = 0;
					k1 = 1;
					i2 = 0;
					j2 = 1;
					k2 = 1;
				} // Z Y X order
                else if(x0 < z0) {
					i1 = 0;
					j1 = 1;
					k1 = 0;
					i2 = 0;
					j2 = 1;
					k2 = 1;
				} // Y Z X order
                else {
					i1 = 0;
					j1 = 1;
					k1 = 0;
					i2 = 1;
					j2 = 1;
					k2 = 0;
				} // Y X Z order
			}

			// A step of (1,0,0) in (i,j,k) means a step of (1-c,-c,-c) in (x,y,z),
			// a step of (0,1,0) in (i,j,k) means a step of (-c,1-c,-c) in (x,y,z), and
			// a step of (0,0,1) in (i,j,k) means a step of (-c,-c,1-c) in (x,y,z), where
			// c = 1/6.

			float x1 = x0 - i1 + G3; // Offsets for second corner in (x,y,z) coords
			float y1 = y0 - j1 + G3;
			float z1 = z0 - k1 + G3;
			float x2 = x0 - i2 + 2.0f * G3; // Offsets for third corner in (x,y,z) coords
			float y2 = y0 - j2 + 2.0f * G3;
			float z2 = z0 - k2 + 2.0f * G3;
			float x3 = x0 - 1.0f + 3.0f * G3; // Offsets for last corner in (x,y,z) coords
			float y3 = y0 - 1.0f + 3.0f * G3;
			float z3 = z0 - 1.0f + 3.0f * G3;

			// Wrap the integer indices at 256, to avoid indexing perm[] out of bounds
			int ii = i % 256;
			int jj = j % 256;
			int kk = k % 256;

			// Calculate the contribution from the four corners
			float t0 = 0.6f - x0 * x0 - y0 * y0 - z0 * z0;
			if(t0 < 0.0f)
				n0 = 0.0f;
			else {
				t0 *= t0;
				n0 = t0 * t0 * grad(perm[ii + perm[jj + perm[kk]]], x0, y0, z0);
			}

			float t1 = 0.6f - x1 * x1 - y1 * y1 - z1 * z1;
			if(t1 < 0.0f)
				n1 = 0.0f;
			else {
				t1 *= t1;
				n1 = t1 * t1 * grad(perm[ii + i1 + perm[jj + j1 + perm[kk + k1]]], x1, y1, z1);
			}

			float t2 = 0.6f - x2 * x2 - y2 * y2 - z2 * z2;
			if(t2 < 0.0f)
				n2 = 0.0f;
			else {
				t2 *= t2;
				n2 = t2 * t2 * grad(perm[ii + i2 + perm[jj + j2 + perm[kk + k2]]], x2, y2, z2);
			}

			float t3 = 0.6f - x3 * x3 - y3 * y3 - z3 * z3;
			if(t3 < 0.0f)
				n3 = 0.0f;
			else {
				t3 *= t3;
				n3 = t3 * t3 * grad(perm[ii + 1 + perm[jj + 1 + perm[kk + 1]]], x3, y3, z3);
			}

			// Add contributions from each corner to get the final noise value.
			// The result is scaled to stay just inside [-1,1]
			return 32.0f * (n0 + n1 + n2 + n3); // TODO: The scale factor is preliminary!
		}

		private static byte[] perm = new byte[512] { 151, 160, 137, 91, 90, 15,
			131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69, 142, 8, 99, 37, 240, 21, 10, 23,
			190, 6, 148, 247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33,
			88, 237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 74, 165, 71, 134, 139, 48, 27, 166,
			77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244,
			102, 143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169, 200, 196,
			135, 130, 116, 188, 159, 86, 164, 100, 109, 198, 173, 186, 3, 64, 52, 217, 226, 250, 124, 123,
			5, 202, 38, 147, 118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17, 182, 189, 28, 42,
			223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9,
			129, 22, 39, 253, 19, 98, 108, 110, 79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 97, 228,
			251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51, 145, 235, 249, 14, 239, 107,
			49, 192, 214, 31, 181, 199, 106, 157, 184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254,
			138, 236, 205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215, 61, 156, 180,
			151, 160, 137, 91, 90, 15,
			131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69, 142, 8, 99, 37, 240, 21, 10, 23,
			190, 6, 148, 247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33,
			88, 237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 74, 165, 71, 134, 139, 48, 27, 166,
			77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244,
			102, 143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169, 200, 196,
			135, 130, 116, 188, 159, 86, 164, 100, 109, 198, 173, 186, 3, 64, 52, 217, 226, 250, 124, 123,
			5, 202, 38, 147, 118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17, 182, 189, 28, 42,
			223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9,
			129, 22, 39, 253, 19, 98, 108, 110, 79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 97, 228,
			251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51, 145, 235, 249, 14, 239, 107,
			49, 192, 214, 31, 181, 199, 106, 157, 184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254,
			138, 236, 205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215, 61, 156, 180 
		};

		private static int FastFloor(float x) {
			return (x > 0) ? ((int)x) : (((int)x) - 1);
		}

		private static float grad(int hash, float x) {
			int h = hash & 15;
			float grad = 1.0f + (h & 7);   // Gradient value 1.0, 2.0, ..., 8.0
			if((h & 8) != 0)
				grad = -grad;         // Set a random sign for the gradient
			return (grad * x);           // Multiply the gradient with the distance
		}

		private static float grad(int hash, float x, float y) {
			int h = hash & 7;      // Convert low 3 bits of hash code
			float u = h < 4 ? x : y;  // into 8 simple gradient directions,
			float v = h < 4 ? y : x;  // and compute the dot product with (x,y).
			return ((h & 1) != 0 ? -u : u) + ((h & 2) != 0 ? -2.0f * v : 2.0f * v);
		}

		private static float grad(int hash, float x, float y, float z) {
			int h = hash & 15;     // Convert low 4 bits of hash code into 12 simple
			float u = h < 8 ? x : y; // gradient directions, and compute dot product.
			float v = h < 4 ? y : h == 12 || h == 14 ? x : z; // Fix repeats at h = 12 to 15
			return ((h & 1) != 0 ? -u : u) + ((h & 2) != 0 ? -v : v);
		}

		private static float grad(int hash, float x, float y, float z, float t) {
			int h = hash & 31;      // Convert low 5 bits of hash code into 32 simple
			float u = h < 24 ? x : y; // gradient directions, and compute dot product.
			float v = h < 16 ? y : z;
			float w = h < 8 ? z : t;
			return ((h & 1) != 0 ? -u : u) + ((h & 2) != 0 ? -v : v) + ((h & 4) != 0 ? -w : w);
		}
	}
}
